This application claims priority to German Patent Application No. 19957793.5 filed Dec. 1, 1999.
The present invention relates to a seat for a means of transport, in particular a vehicle seat, comprising a seat part, a backrest, a backrest adjustment system which connects the backrest to the seat part and which permits a forward pivoting of the backrest onto the seat part, a height adjustable headrest which is displaceably guided via at least one guide rod in an associated guide receiver in the backrest, and retaining means which are effective between at least one guide rod and the associated guide receiver and through which the guide rod is releasably fixable at different heights against displacement.
In two-door motor vehicles, the backrests of the front seats are usually made to pivot forwardly to make it easier to get into the back seats. In vehicles with a low height such as sports cars, the headrest can come into contact with the vehicle roof or the sun visor during this movement. The forward pivoting of the backrest can be made more difficult or even prevented in this way. The set height of the headrest can also be changed.
It is the object of the invention to provide a seat of the kind initially mentioned in which these problems do not occur and wherein in particular contact between the headrest and the vehicle roof should be avoided during the forward pivoting of the backrest.
This object is satisfied by the guide receiver for the guide rod being formed so as to be retractable together with the guide rod opposite to the extension direction of the headrest inwards into the backrest into a recessed position and back out again while the guide rod is arrested by the retaining means relative to the guide receiver and by means being provided through which an automatic inward movement of the guide receiver is caused by the forward pivoting of the backrest and an automatic outward movement of the guide receiver back into its original position is caused when the backrest is pivoted back.
Due to the automatic inward movement of the guide receiver while the backrest is pivoted forwardly, a low position of the headrest is also achieved when this was previously set to a greater height. Contact of the headrest with the vehicle roof during the forward pivoting of the backrest can thereby be effectively prevented. The headrest can be retracted so far until the headrest contacts the upper side of the backrest, that is possibly further than its lowest setting position in which the headrest still has a small spacing to the upper side of the backrest. The amount the headrest protrudes upwardly over the backrest is thereby reduced to a minimum so that contact with the vehicle roof can also be avoided with very low vehicles. The guide receiver is here also stopped via the retaining means so that the set headrest height does not change.
The inward movement of the guide receiver with the guide rods being held in place by the retaining means with respect to the guide receiver, at the same time ensures that the headrest position does not change relative to the guide receiver during retraction. When the guide receiver is again extended back into its starting position, the previously set headrest position is therefore again reached. Thus, no new setting is required. Nevertheless, the setting capability of the headrest height is maintained without restriction over the whole setting range.
In accordance with an embodiment of the invention, at least one force deflection system having a flexible force transmission element is active between the backrest adjustment system and the guide receiver for the retraction and/or extension of the guide receiver. A Bowden cable can in particular serve to move the guide receiver inwardly and/or outwardly. Such a system requires little construction effort and can be accommodated in the seat in a space-saving manner. Moreover, due to the flexibility of the force transmission element, it allows a combination with an active head rest system in which the headrest is moved from its normal position into a position displaced upwardly and forwardly in the event of a rear-end impact.
The force transmission element preferably acts on the guide receiver in the extension direction while an elastic return device is provided which acts on the guide receiver in the retraction direction. The construction effort is reduced by the use of an elastic return device and the return force is advantageously supported by gravity since the return device acts on the guide receiver in the retraction direction, that is approximately in the direction of gravity. The return element can be given lower dimensions as a result. However, the reverse arrangement is also possible.
It is also preferred for the one end of the inner cable of the Bowden cable to be fixed to a stationary backrest part and for the associated end of the sleeve of the Bowden cable to be fixed to the guide receiver. A reverse arrangement is also possible here. The other end of the sleeve of the Bowden cable is in particular fixed to a stationary part of the backrest adjustment system and the other end of the inner cable is fixed to a part of the backrest adjustment system which is movable with the backrest when this is pivoted forwardly, with this end of the inner cable being attached to the movable part of the backrest adjustment system in such a way that the Bowden cable is relieved when the backrest is pivoted forwardly. This means that the Bowden cable is stressed at the normal backrest position and its sleeve fixes the guide receiver in its topmost position. When the backrest is pivoted forwardly, the Bowden cable is relieved and the return element can move the guide receiver into a recessed position.
In accordance with a further embodiment of the invention, the end of the inner cable at the backrest adjustment system side is attached to a slide block which is displaceably guided between two end positions in a slide track arranged on a stationary part of the backrest adjustment system, with the slide block being moved to and fro between its two end positions by a part of the backrest adjustment system moved by the backrest when this is pivoted forwardly. A pressure element is in particular arranged at the moved part of the backrest adjustment system, said pressure element holding the slide block in its end position in which the Bowden cable is stressed when the backrest is in its upright position and successively releasing the slide block when the backrest is pivoted forwardly so that the slide block can move into its other end position.
The movement of the Bowden cable is advantageously limited by the slide track. Together with the pressure element, the advantage also results that the backrest has a freewheel mechanism during pivoting forward. That is, the backrest can be completely pivoted forwardly without any impediment by the Bowden cable even when the inward movement of the guide receiver has already been stopped. The slide block, namely, then comes to stop at its position in the slide track and the pressure element moves away therefrom. When the backrest is pivoted back, the pressure element then acts on the slide block again from a certain inclination of the backrest and moves it back into its starting position in which the Bowden cable is stressed.
This is in particular of advantage when, in accordance with a further embodiment of the invention, a path multiplier is arranged between the backrest adjustment system and the guide receiver, said path multiplier translating a small pivot angle of the backrest into a large path of the guide receiver for the headrest. With this embodiment, it can be achieved that a small forward-pivot angle of the backrest, in particular an angle of approximately 15xc2x0, already results in the complete retraction of the headrest, even when set to its highest position. It is thus reliably ensured that the headrest does not come into contact with either the vehicle roof or a visor which may possibly be turned down.
The transmission ratio can also be selected such that it changes with the pivot angle of the backrest. The inward movement of the headrest can thus be effected in a slower manner at the start and/or end stage in order to protect the system components against too great a strain.
Two Bowden cables are preferably provided whose one end is in each case fixed to the path multiplier and whose other end is fixed to the guide receiver or the backrest adjustment system. A path multiplication between the pivot angle of the backrest and the displacement path of the guide receiver can be realised in a very simple manner in this way.
In accordance with a further embodiment of the invention as a path multiplier, a transmission can in particular be provided which comprises two coaxially journalled rotating wheels which are connected to one another in a rotationally fixed manner, which have different diameters to one another and where the one end of the inner cables of the two Bowden cables is respectively fixed in place on the periphery of said rotating wheels such that the inner cables of the two Bowden cables can be wound onto and off the rotating wheels in opposite directions. Such a step-up gear is low in construction effort and reliable in operation in combination with a Bowden cable.
In accordance with a further embodiment of the invention a spring actuator can be provided between the backrest adjustment system and the guide receiver. Excessive strain on the system parts can also be avoided by such a spring actuator. It is also generally possible with such a spring actuator as an alternative to the arrangement with slide block and pressure element to compensate for different headrest heights before retraction into the guide receiver.
In accordance with a further embodiment of the invention, a sleeve is provided in which the guide receiver is displaceably guided and which is fixable in the backrest, with the guide receiver in particular forming an inner sleeve into which a guide rod is insertable and fixable at different heights and which is itself displaceable in the outer sleeve stationary on the backrest. A compact arrangement with a reliable function can be provided in this way.
One end of the sleeve of a Bowden cable preferably acts on the guide receiver and the associated end of the inner cable of said Bowden cable acts on the sleeve, with a spring acting between the sleeve and the guide receiver and loading the guide receiver in the retraction direction. This results in a system which can be installed completely into a backrest of a vehicle seat, with the sleeve being attachable to the backrest by conventional means, for example by latching. The use of a sleeve ensures a reliable and repeatable inward and outward movement of the guide receiver.
In accordance with a further embodiment of the invention, an abutment for the lower end of the guide rod is provided which limits the inward movement of the guide rod and thus of the guide receiver. In this way, the headrest can be moved into a desired retraction position which is independent of the actual backrest when the backrest is pivoted forwardly.
In accordance with a further embodiment of the invention, the headrest is automatically adjustable to a minimum height while the guide receiver is moving inwardly. This can be effected in particular by the retaining means acting between the guide receiver and the guide rod being made automatically releasable over a certain range. For example, a mechanical latching in this range can act only in one direction so that the guide receiver can still be further retracted by a certain number of latch positions when the headrest abuts its lowest position. It is achieved in this way that when the headrest is extended again, it returns to at least a height which ensures a sufficient protective effect for the greater majority of the population.
In accordance with a further embodiment of the invention, the guide receiver can be extended out of the backrest as part of an active head support system together with the guide rod in the event of a rear-end impact and into such a position that the headrest is brought into a forwardly and upwardly displaced position. The headrest retraction in accordance with the invention can thus be advantageously combined with such an active head support system which offers additional safety, with the guide receiver preferably being extendable out of the backrest by an outward movement of the sleeve. This requires little construction effort and can be combined particularly well with existing active head support systems.